-Styles must be improved (full width for smartphones, ...)
PGN text is not selectable (understand why?!)
-Change cursor when computer "think" (sablier)
-Tooltip text should fade (even when mouse stay on it, especially for small screens)
Checkered stage 2: switch button at reserve position (or on top).
Mode expert: game.js, button on top (with online indicator)
Turn indicator on top too (black or white)